# Mazda Rotary Engine

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#### rv7charlie

##### Well-Known Member
He's on Flyrotary, and has reported on a lot of his research there. Same guy who found the likely cause of short spark plug life in a/c rotaries, and found that after adding a controllable prop, he could suspend his research into adding a turbo to his engine (his airport elevation is around 5K feet), and found that the 3rd intake port on a 6 port Renesis is useless below about 6500 rpm, and etc etc.

#### Urquiola

##### Well-Known Member
If I can mention something not previously mentioned (unless I missed it, if I did I apologize) eliminating overlap which is in Most engines unless running Hydrogen, the overlap lets fresh air in to helps evacuate (flush-out) the exhaust. A problem arises is when that fresh air also contains fuel, which burns in the exhaust, helping to perpetuate the theory that the Rotary is a HOT engine. As Tracy discovered a delayed fuel charge helps eliminate that (as does Fuel Injection), although not entirely as the unburned fuel in the squish areas of the Rotor are flung out the Peripheral Exhaust Port by the Apex seals - this is eliminated mostly in the RX8 with side exhaust ports and any fuel is carried into the next combustion event.
Side Intake and exhaust ports are restrictive in their natural state and can be improved with Port and polishing but they still have a square edge - thus turbulence restricting flow. Peripheral Ports are straight-in and Straight-out
Nothing it seems is perfect, but selecting the better option is still the debate.
Hope that helps those unfamiliar with the different configurations.
George
Form the books by Harry Ricardo, patriach of ICE, you can guess that one of reasons for the hot exhaust gases in Wankel RCE is not the loss of fresh mix into exhaust, plus the thermal reactor added to reduce emissions, but a low MEP, a low effective compression ratio, see figures in Wikipedia MEP article.
Early engines, when origin of detonation, and the ON, was unknown, had very low CR, extremely hot exhaust gas temperatures, as a result, exhaust valves needed frequent replacement.
An article in Wankel News, by Reiner Nikulski, shows same happens in Sachs KC-27 air cooled housing, charge cooled rotor Wankel, 294 cc per chamber; at full charge, top torque regime, exhaust gas temperature is lower than at part load, this engine has no air injection in ports, no thermal reactor, no catalizer.
The results of eliminating port overlap are well described in the cited SAE papers, but I can't invite you to these references, it are copyrighted.
My feeling is the best combination for Wankel is a Reed Valve controlled, rectangular or square peripheral intake port, and exhaust ports in both side plates, I failed in finding figures of performances, economy, emissions for this arrangement.
Blessings +

#### Lendo

##### Well-Known Member
It has been suggested to me the best PP inlet is thin and wide, as it reduces overlap, as it can't be too wide perhaps a flat bottom with a rounded top.
George

#### Erik Snyman

##### Well-Known Member
It has been suggested to me the best PP inlet is thin and wide, as it reduces overlap, as it can't be too wide perhaps a flat bottom with a rounded top.
George
Or, you can hang the old IO-470 on the nose. Check oil, check fuel, and go fly.
Sorry, couldnt resist.
Erik in Oz.

#### dwalker

##### Well-Known Member
HBA Supporter
Or, you can hang the old IO-470 on the nose. Check oil, check fuel, and go fly.
Sorry, couldnt resist.
Erik in Oz.
Why would I want an antique heavier engine with less power?

Sorry! Couldn't resist!

#### Lendo

##### Well-Known Member
What I was saying there are all sorts of opinions on Mazda Rotary mods for Aviation, but I personally don't know the best.
I will say however the Rotary could be conceivably the best 'Power to Weight Ratio' for Aviation with the right mods, Mistral and Powersport did wonderful work with the engine. It does require a PSRU and a good reliable one and small demand don't equate to large profits -sadly.
Who was it that said if you want to make a small fortune out of Aviation, you must start with a large fortune.
George

#### Powersport Aviation

##### Member
While it is always fun to read everyone's point of view, I prefer actual proof. We at Powersport have never had a leak around our PP and there are very good ways to assure this. Further the reason for PP in our rotary is so that we can produce currently 250+ HP in a fully installed 325lb package.

#### dwalker

##### Well-Known Member
HBA Supporter
While it is always fun to read everyone's point of view, I prefer actual proof. We at Powersport have never had a leak around our PP and there are very good ways to assure this. Further the reason for PP in our rotary is so that we can produce currently 250+ HP in a fully installed 325lb package.
That is interesting. Just curious-

What RPM are you making 250HP at?
How many hours have you run these engines?

I find it exceedingly interesting that pretty much all the worlds best PP builders- acknowledge that the PP WILL eventually leak coolant into the combustion chamber, so your claim is intriguing. Perhaps it is the difference in power output, or time in service.

#### Cardmarc

##### Well-Known Member
While it is always fun to read everyone's point of view, I prefer actual proof. We at Powersport have never had a leak around our PP and there are very good ways to assure this. Further the reason for PP in our rotary is so that we can produce currently 250+ HP in a fully installed 325lb package.
At what rpm on the 13B rew(?) and torque is that 250 HP produced. Can you publish engine dyno curves for us?

#### rv7charlie

##### Well-Known Member
Are new engines currently available? Are they more affordable than they were back when I took the survey & got the T-shirt at OSH (>20 yrs ago)?
Which engine controller; the old Bendix style injection that was being installed back then, or a modern automotive style (dual) controller?

The market would be there, if the package was affordable (meaning in the same price range as a mid-time Lyc; not higher than a new Lyc) and it was getting some higher profile exposure to the masses.

Charlie
(rolling my own Renesis installation)

#### dwalker

##### Well-Known Member
HBA Supporter
While it is always fun to read everyone's point of view, I prefer actual proof. We at Powersport have never had a leak around our PP and there are very good ways to assure this. Further the reason for PP in our rotary is so that we can produce currently 250+ HP in a fully installed 325lb package.
I also have to add that perhaps you did not mean to, but that "actual proof" line seems a bit snarky.

I live in the world of reality when it comes to engines and thier claims, I worship at the alter of results and believe the gospel of the dyno above all else. I have a LOT of experience with PP, Semi PP, and all sorts of bridge, half-bridge, J, mail slot, cheesegrater, and other port types that have been used on the various forms of 13B rotary over the years.

I ONLY care about what I can buy or build, today, for less than the cost of of a spanky new engine.
Today, in my warehouse, I have both semi-p and standard port 13B-REW housings ready to be built into flight engines.
Today I have a Renesis rotating assembly at the machinist getting prepped for the above housings.
Today I have the Ross PSRU which is in nearly new condition and ready to go

Today I am tired of hearing about vaporware, parts that do not exist unless a hefty deposit is placed and a long, long wait ensues, and theory.
Boost works. Actual modern EFI works. The rotary works if we get out of its way and let it.

#### rv7charlie

##### Well-Known Member
That's impressive. And it only costs a little more than a 200+ HP Lyc/Cont, with the bonus of a complete roadworthy vehicle thrown in as a bonus. ;-) We now have a use for 3:1 reduction drives, too.

I'd love to see a bit more info on the motor itself; it sounds a bit much like the old 'charge cooled' designs that actually achieved the rotary's terrible *reputation* for bad BSFC.

#### Lendo

##### Well-Known Member
Yep! it's the same Motor alright, or redeveloped motor by Brian Crighton who developed the Norton Rotary Motor for racing. I didn't know who he was until I looked up the Norton Rotary history .
The biggest issue here is the RSRU ratio needed for Aircraft use. Probably run at 8,000rpm to 9,000 rpm with something like a 3.5: 1 ratio PSRU
George

#### Lendo

##### Well-Known Member
rV7charlie, I believe air cooled Rotor, it may be charge cooled - not sure.

I had a look at the Powersport Page and a lot of old information and photos, but can't see anything new to get excited about. One of the of the real problems is running out of new components and prices are going through the roof. If Mistral were alive to day they would need to be developing their own engine parts for Certification and Audit Trail.

Locally there is a chap making Al end housing and Rotors for racing, but they don't care how long they last, they just buy new stuff when it's needed.

If someone were talking Ceramic components, like housings (expensive), Titanium or Carbon Rotors it would soon get my interest. If you were going to go to the trouble to make Housings, it's much easier to include things like P-ports and direct injection sites, removing cross contamination of inlet and outlet. Even redirected cooling passages, such as the original Powersport people trialed.

All this requires the 'where with all' and extensive knowledge and experience.
George

#### Cardmarc

##### Well-Known Member
Ceramic rotor seals are available

#### Lendo

##### Well-Known Member
Cardmarc- Understood!

#### Lendo

##### Well-Known Member
rv7charlie, The later Norton Changed from air fuel (charged) cooling to later, just air through the Rotor but because air wasn't enough they used liquid cooling the whole housing. This updated engine would be the same I assume, it's only 42.1 cu/inch which is only 52.6% of the Mazda Rotary 80 cu/inch. The exhaust through venturi rammed air effect makes a significant and proven difference, as shown in the Norton Performance (a free Turbo).
If you use a 3:1 PSRU Ration you wouldn't be able to go past 8,500 rpm/5252 =1.161843*42.1 = 68.136 hp but with forced induction it must be about 180 hp you would probably be the max to expect. 8500/3:1 = 28333 prop rpm. Cruise probably be 6,500 to 7,000 rpm and still good HP.
George

#### dwalker

##### Well-Known Member
HBA Supporter
rV7charlie, I believe air cooled Rotor, it may be charge cooled - not sure.

I had a look at the Powersport Page and a lot of old information and photos, but can't see anything new to get excited about. One of the of the real problems is running out of new components and prices are going through the roof. If Mistral were alive to day they would need to be developing their own engine parts for Certification and Audit Trail.

Locally there is a chap making Al end housing and Rotors for racing, but they don't care how long they last, they just buy new stuff when it's needed.

If someone were talking Ceramic components, like housings (expensive), Titanium or Carbon Rotors it would soon get my interest. If you were going to go to the trouble to make Housings, it's much easier to include things like P-ports and direct injection sites, removing cross contamination of inlet and outlet. Even redirected cooling passages, such as the original Powersport people trialed.

All this requires the 'where with all' and extensive knowledge and experience.
George
Well, here is a can of worms worthy of a completely new discussion, but let me throw aa few things out-

A long time ago, Mazda did a bunch of testing with various anti-wear/low friction methods other than chrome plating for the rotor housing surface and nitriding for the iron plates. They ended up with a Nikasil coated steel liner and irons as the most practical option, along with a "cermet" treated rotor housings. The problem with the Nikasil and Cermet coatings was the break in. Basically, the housings had to be burnished before the seals were installed, and even then initial wear could be extreme. Now, that was with older materials so that has certainly changed, but neither process is practical in a production car.
In the 2000's forward the UAV industry liked the rotary engine since it ran so smooth and allowed a much more vibration free camera platform. They did a large amount of development and ended up back where Mazda did, with Nikasil or Cermet coatings, along with more modern seals, including ceramics.

In my shop I had a set of worn out rotor housings stripped of thier chrome plating and coated with Nikasil to just over 10thou, and a set of irons surface ground 10 under with Nikasil built back up to standard. I put the motor together with stock apex seals and ran it for 1000miles to break it in/burnish the Nikasil. When I took it apart the seals were abnormally worn. This is because the Nikasil surface is rough and very hard, and where a piston ring wears slightly in a Nikasil bore, the spring pressure and seal construction of the apex and side seals are simply not durable enough. the same thing was noted with CERMET housings that Pineapple did up until about 2010 or so. I re-assembled the engine with new seals and after 100 miles the compression was slightly above average and continued to improve. At 5000 miles I tore the engine down again and there was no wear noted. The apex seals had burnished in slightly but the housings and irons looked the same as they had. I sold the engine to a customer and a few years later at around 60K miles I tore the same engine down with no measurable wear noted again. This is noteworthy because this was an engine fitted to an S4 Turbo 2 that made about 300whp, was driven almost every day, and was abused by its owner. At one point the owner discovered the OMP lines had broken and there was little if any oil being injected into the engine, and he had several overboost events that should have caused major damage, but did not.

So, in reality the technology is out there now to create amazingly durable 13B engines with more modern components, but the cost is somewhat high. Also, I think the fellow in Canada that did the CERMET housings is no longer offering it. Nikasil can be tricky and if not done exactly right it can and will "peel" from the substrate metal.
In an aircraft the added strength and durability might be worth the trouble, or maybe not.